Washing, cleaning, and caring for the human body is an important basic need, and cosmetics manufacturers are always eager to satisfy the continuously changing and evolving needs of the consumers by providing new and/or improved products.
One fundamental component of daily hygiene is, for example, the effective elimination or at least the significant reduction of body odor and/or perspiration odor. These odors are created by the bacterial decomposition of various components of human (apocrine) perspiration on the skin, during which, among other things, low fatty acids (in particular C4-10 fatty acids), ammonia, amines, indoles and sulfurous substances are created.
To combat body odor and/or perspiration odor, products are offered commercially in a wide variety of forms of application, such as powders, sticks, aerosol sprays, pump sprays, liquid and gel-like roll-ons, creams, gels, and saturated flexible substrates (known as deodorant wipes).
One variant of deodorant and antiperspirant compositions that is particularly preferred by many consumers is propellant-operated aerosol sprays.
These are characterized by convenient handling and dosability, hygienic use, and consistent effectiveness of the content sealed off from the outside atmosphere.
Commercially available aerosol dispensing devices always comprise an aerosol can and a spray head. They are pressurized and include propellant.
This system is necessary to ensure that the spraying properties are preserved over the entire usage duration of the aerosol spray. Otherwise, it would be possible for valves to clog, for example.
The disadvantage of antiperspirants of the aerosol type is that these often have a lower antiperspirant effectiveness compared to roll-ons or antiperspirant sticks.
The reason for this is that at times only approximately 20% of the required amount of antiperspirant active ingredients (usually astringent aluminum salts) from the aerosol compositions are delivered to the skin in a customary spray application.
Astringent aluminum salts are often present in antiperspirants in particulate form in a hydrophobic carrier (comprising at least one oil). The oil or oils of the hydrophobic carrier improve the adhesion of the suspended components to the skin, and moreover, serving as solvents, lubricants and spreading agents, help to uniformly distribute the antiperspirant agent on the skin.
Particulate active ingredients tend to precipitate from hydrophobic carriers, settle or agglomerate during storage. To prevent this, and to ensure stable suspension of the particulate active ingredients in antiperspirants over a long period of time, hydrophobically modified silicates, especially phyllosilicates such as montmorillonite, kaolinite, illite, beidellite, nontronite, saponite, hectorite, bentonite, smectite and/or talcum, are usually added to the carriers as suspending agents.
It was proposed in EP 570085 A2 to use propylene carbonate as an activator for hydrophobically modified clay materials in antiperspirants comprising a hydrophobic carrier.
The polar property of the propylene carbonate enables optimal dispersion of the hydrophobically modified phyllosilicates in anhydrous media. In this way, a viscosity is achieved, which is required for the stable suspension of particulate antiperspirant substances, and in particular of astringent aluminum salts, in the carrier oil.
The weight ratio of the propylene carbonate to the hydrophobically modified phyllosilicate is usually 1:3 (see also U.S. Pat. No. 3,773,683 and U.S. Pat. No. 4,904,463).
Despite the addition of propylene carbonate (at the above-mentioned weight ratio to the phyllosilicate), however, the above-mentioned delivery rate of antiperspirant active ingredients to the skin was not always satisfactory for conventional spray applications made of anhydrous aerosol antiperspirant compositions.